The present invention relates to a method for calibrating fully and semi-automatic particle counters used in hemocytologic analysis to a specific species. The present invention further relates to compositions that can be employed in calibrating such counters so that the counters can be used in the accurate analysis of blood from different species.
It is well accepted in the medical field that a count of various cellular elements in blood can be correlated to certain disease states in humans. The use of hemocytometer counting chambers provides the ability manually to quantitate the cellular elements in a blood sample from a subject. Presently, there are also available fully- and semi-automated particle counters for use in making such blood analyses in human medicine, including counters manufactured by Coulter Electronics, Inc., of Hialeah, Fla. The wide use of counters in human blood analysis is evidenced by the development of human counter solutions and calibration procedures for such counters, which solutions are the subject of U.S. Pat. Nos. 4,250,051 (Armstrong) and 3,406,121 (Jones).
Fully automated counters are the rule in human medicine today. It is common medical diagnostic procedure to analyze and test the blood sample of a patient in order to make certain classic determinations with respect to the blood sample. This procedure is an acknowledged, important aid to a physician. The characteristic parameters monitored include red blood count (RBC), white blood count (WBC), hematocrit (HCT), hemoglobin (Hgb), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC). As noted above, Coulter Electronics, Inc. and other manufacturers sell several models of blood cell counting and analyzing instruments which are well-known in human medicine. Instruments are available which will accept a patient's blood sample and process the same sample automatically and continuously to provide one or more of the aforementioned parameters.
As disclosed by Armstrong, operation of an automatic counting instrument of the type commonly used for human blood analyses requires periodically confirming that the instrument's performance still conforms with the counting parameters internally pre-set when the instrument was placed in operation. This periodic confirmation of predetermined instrument values, which will hereinafter be called "standardization," is carried out by running a composition or "control" similar in nature to that of blood samples routinely encountered, through an instrument for which the counting parameters have previously been established, that is, through an instrument which has already been "calibrated." By evaluating the instrument's readings for the control against the control's known characteristic parameters, the user obtains a check on the continued precision of instrument in adhering to the pre-set calibration values.
Heretofore, the calibration values themselves were established by what Armstrong describes as "reference procedures." Routinely, specimens of fresh blood drawn from as many as 20 or more donors were divided into multiple aliquots and cycled through a particular instrument to obtain an average value and deviation standard for each characteristic parameter. Thereafter, the instrument was adjusted internally ("calibrated") so that the range of each counting parameter coincided with the "normal" range defined by the average and standard deviation of the corresponding characteristic parameter for the blood samples. Whether the instrument remained within these calibrated ranges had to be monitored regularly by the above-described standardization procedure.
While controls were available in the prior art for the latter procedure, a calibration method of like simplicity and general applicability was not available. In accordance with the present invention, however, there are provided an improved process for non-human blood analysis and a method of preparation of a calibrator solution of the particular species under examination for calibrating fully- and semi-automated particle counters. The inventors, Barry T. Mitzner, Doctor of Veterinary Medicine in the State of Florida, and Colin F. Aldersley, a licensed medical technologist within the State of Florida, have found that the use of human counter solutions and calibration procedures to analyze non-human blood can result in inaccurate counts by up to 30%. Also, conventional calibration procedures are impracticable for veterinary application, being too time consuming and prone to inaccuracies by virtue of the numerous dilutions they entail.